An analog-to-digital converter (ADC) is an electronic device that converts analog signals to digital signals. In essence, an ADC converts an analog voltage or current input to a digital number representing the magnitude of the voltage or current input. The digital output is typically a two's complement binary number that is proportional to the voltage or current input.
The resolution of an ADC indicates the number of discrete values it can produce over the range of analog values. The resolution determines the magnitude of the quantization error, and thus dictates the maximum possible average signal-to-noise ratio for an ideal ADC without the use of oversampling (i.e., sampling at a higher rate). The values are usually stored electronically in binary form. As such, the resolution is typically expressed in number of bits, and the number of discrete values (or levels) available within an ADC is assumed to be in a power of two. An ADC with a resolution of, for example, 8 bits can encode an analog input to one in 28=256 different discrete values (or levels). The discrete values can represent the ranges from 0 to 255 (as unsigned integers) or from −128 to 127 (as signed integers), depending on the application.
An ADC typically provides a quantization step size that is several times smaller than the accuracy required in the physical value that is being measured through that ADC. With oversampling and filtering, it is possible to improve the resolution of the measurement at the output of the filter, thereby increasing the effective number of bits of the ADC.
The present disclosure provides an improved method and apparatus for increasing the effective resolutions of ADCs.